Term
|
Definition
|
|
Term
|
Definition
A very hot ball of gas formed when gravity pulls the gas and dust particles together. |
|
|
Term
|
Definition
When two Hydrogen atoms are fused together and form Helium because of the pressure. This nuclear reaction is called fusion and results in the release of vast amounts of energy. The star stops shrinking because the gravitational force and pressure created by the fusion reactions are balanced. Small stars burn fuel slower than big stars and have longer stable periods. |
|
|
Term
|
Definition
| When a star runs out of Hydrogen fuel in its core it will start to contract again. The remaining nuclear fuel in the skin of the star starts to undergo fusion and causes the star to expand. |
|
|
Term
|
Definition
Large dying stars literally explode when they run out of nuclear fuel. Only the dense core of the star remains. |
|
|
Term
|
Definition
| The remaining core of a large star so dense that protons and electrons fuse together to make neutrons. |
|
|
Term
|
Definition
| The remains of a really large star ay leave an incredibly dense core which has such a powerful gravitational field that even light cannot escape from it. |
|
|
Term
|
Definition
| Small stars which run out of nuclear fuel or were never big enough to undergo nuclear fusion gradually cool. |
|
|
Term
| What is the life cycle of a small star? |
|
Definition
| Nebula → protostar → stable star → red giant → dwarf star |
|
|
Term
What is the life cycle of a large star |
|
Definition
Nebula → protostar → stable star → red giant → supernova → neutron star or black hole |
|
|
Term
|
Definition
| A star system is a star and the various objects which orbit that star like planets, natural satellites, comets and asteroids. |
|
|
Term
|
Definition
| A galaxy is a collection of stars which in astronomical terms are close together. For example our star, the Sun and ourselves, are part of the milky way galaxy. However the closest star to us in this galaxy is still 4 light years away! |
|
|
Term
|
Definition
| Everything that exists! All the galaxies from our one universe. |
|
|
Term
| How does a protostar form? |
|
Definition
| An event like a supernova causes a region of gas to clump. The gravitational forces betwwen the gas particles cause it to shrink further. As this happens the as gets hotter and hotter. A protostar has been formed. |
|
|
Term
| What is the difference between a protostar and a stable star? |
|
Definition
The hot ball of gas called a protostar eventually becomes so hot and dense due to the gravitational forces that the hydrogen nuclei start to bond together and form helium nuclei. This is called nuclear fusion, when this occurs it is no longer a protostar but now a stable star in the main part of its cycle. |
|
|
Term
| Why does a satble star stay the same size? |
|
Definition
| The gravitational force trying to shrink the satr are balanced by the outwards pressur ecaused by the nuclear fusion reactions. |
|
|
Term
| Why does a stable star become a red giant? |
|
Definition
| In the core of a star coming to the end of its stable stage it will run out of the hydrogen fuel required for nuclear fusion, the star will shrink but then the outer part of the star will start to undergo nuclear fusion causing the star to expand before gravitational forces overcome this and make the star shrink again. This process is repeated a number of times. |
|
|
Term
| Why do small stars become brown dwarfs? |
|
Definition
Eventually small stars simply run out of suitable fuel for nuclear fusion. The stars gradually cools and changes colour eventually becoming a brown dwarf, a relatively cool star. (Some protostars are too small for nuclear fusion to even start and jump striaght to this stage - not needed for syllabus or exam.) |
|
|
Term
| What are artificial satellites used for? |
|
Definition
| Telecommunications, weather and geographical observations, spying, global positioning and astronomical telescopes. |
|
|
Term
Describe the orbits of a polar orbit satellite. What are polar orbit satellites used for? |
|
Definition
Polar satellites arbit across the north and south pole of the Earth. Their orbit time can be changed depending on its speed. Polar satellites are used for making weather and geographic observations as well as spying! |
|
|
Term
Describe the orbit of a geostationary satellite. How long does it take a geostationary satellite to complete one rotation? What are geostationary satellites used for? |
|
Definition
A geostationary satellite stays above one place on the Earth's surface. Therefore it takes 24 hours for a geostationary to complete one rotation just like the Earth. Geostationary satllites are primarily used for telecommunications and global positioning systems. |
|
|
